This proposed research has two aspects: 1. We have recently shown that the concanavalin A receptor (presumably a glycoprotein) in the membrane of embryonic amphibian muscle cells can be electrophoretically redistributed by small, externally applied electric fields. I propose to quantitatively measure this redistribution in order to get precise information about the electrophoretic mobility and diffusion coefficient of this membrane constituent. Further I intend to get information about the nature of the receptor and the membrane by measuring the rate of redistribution of the receptor as a function of external parameters such as pH, calcium ion concentration and temperature. I also intend to do similar measurements on other, better defined membrane components such as the acetylcholine receptor. 2. Preliminary measurements show that electrical current enters early cleavage embryos at the region which will become the cleavage furrow. Shortly after cleavage, this current reverses and then leaves the furrow. These results were obtained by us from sea urchin and frog embryos. I propose to build a vibrating probe at the Marine Biological Laboratory in order to further study these currents. The ionic, spatial, and temporal character of the currents will be explored with the aim of understanding their role in cytokinesis. I would particularly like to establish if they are causal or are a secondary consequence of other events.